The preparation of dinitriles, such as ADN, from mononitriloolefins, such as PN, utilizing zerovalent nickel catalysts with or without a catalyst promoter is widely practiced in the art. The preparation of ADN from PN is of particular interest because ADN is an intermediate used in the production of hexamethylenediamine which is in turn used to produce polyhexamethyleneadipamide, a commercial polyamide useful in forming fibers, films and molded articles.
U.S. Pat. No. 2,571,099, issued on Oct. 16, 1951 to Paul Arthur, Jr. et al. discloses the use of nickel carbonyl with or without the addition of a tertiary aryl phosphine or arsine. This process produces a relatively high percentage of undesirable polymeric products when applied to nonconjugated olefinic starting materials and a relatively poor yield in all cases.
U.S. Pat. No. 3,496,215, issued on Feb. 17, 1970 to W. C. Drinkard et al., discloses an improvement in nickel-catalyzed hydrocyanation wherein triarylphosphite ligands are utilized and carbonyl ligands are eliminated, thereby dramatically reducing polymer formation and generally increasing yield to desirable nitrile products.
The teaching of the use of a promoter in the hydrocyanation reaction appears in U.S. Pat. No. 3,496,217 issued on Feb. 17, 1970 to W. C. Drinkard et al. This patent discloses an improvement in hydrocyanation using a promoter selected from a large number of metal cation compounds with a variety of anions as catalyst promoters. More particularly, the patent discloses as a promoter a cation of zinc, cadmium, beryllium, aluminum, gallium, indium, silver, titanium, zirconium, hafnium, germanium, tin, vanadium, niobium, scandium, chromium, molybdenum, tungsten, manganese, rhenium, palladium, thorium, erbium, iron and cobalt, or mixtures thereof. Preferred anions are halide, i.e., fluoride, chloride, bromide, and iodide; anions of lower fatty acids of from 2 to 7 carbon atoms, HPO.sub.3.sup.-2, H.sub.2 PO.sub.2.sup.-, CF.sub.3 COO.sup.-, OSO.sub.2 C.sub.7 F.sub.15.sup.-, and SO.sub.4.sup.-2, etc. The known organometallic compounds (C.sub.2 H.sub.5).sub.3 Al.sub.2 Cl.sub.3, and C.sub.2 H.sub.5 AlCl.sub.2 are also disclosed as promoters.
U.S. Pat. No. 3,496,218 issued on Feb. 17, 1970 to C. W. Drinkard discloses a nickel hydrocyanation catalyst promoted with various boron-containing compounds, including triphenylboron and alkali metal borohydrides.
U.S. Pat. No. 3,925,445 issued on Dec. 9, 1975 to C. M. King et al. discloses zerovalent nickel hydrocyanation catalysts promoted with metal halides and organoboron compounds.
U.S. Pat. No. 3,852,325 issued on Dec. 3, 1974 to C. M. King teaches that along with production of 3-pentenenitrile (3PN) in the hydrocyanation of butadiene there is also obtained varying amounts of cis- and trans-2-pentenenitriles (C-2PN and T-2PN) and that these 2-pentenenitriles are found to be detrimental to catalyst efficiency in the hydrocyanation of 3PN or 4-pentenenitrile (4PN) to adiponitrile (ADN). The patentee also teaches that T-2PN cannot be removed satisfactorily from a mixture of pentenenitriles by fractional distillation, for example, because its boiling point is too close to that of other pentenenitriles such as 3PN or 4PN. Isomerizing T-2PN to the more volatile C-2PN which in turn can be removed from the reaction mixture by fractional distillation is discussed.
U.S. Pat. No. 4,774,353 issued on Sept. 27, 1988, discloses a process for the preparation of dinitriles, e.g., ADN, from unsaturated nitriles, e.g., PN, in the presence of a zerovalent nickel catalyst and a triorganotin catalyst promoter having the general formula ##STR1## wherein R.sup.1, R.sup.2 and R.sup.3 are the same or different and are selected from groups consisting of alkyl and substituted aryl groups of 6 to 16 carbon atoms. One or more of the substituent groups in the substituted alkyl and aryl groups may be selected from fluoro or alkoxy groups having 1 to 8 carbon atoms, trialkylsilyl groups with alkyls having 1 to 6 carbon atoms, cyanoalkyl groups having 1 to 20 carbon atoms, and sulfonato. The anion X is a non-nucleophilic ion, the conjugate acid of which has a pK.sub.a less than about 4.